The Collaborative International Dictionary of English v.0.48:

Wither \With"er\, v. i. [imp. & p. p. Withered; p. pr. & vb.
   n. Withering.] [OE. wideren; probably the same word as
   wederen to weather (see Weather, v. & n.); or cf. G.
   verwittern to decay, to be weather-beaten, Lith. vysti to
   wither.]
   [1913 Webster]
   1. To fade; to lose freshness; to become sapless; to become
      sapless; to dry or shrivel up.
      [1913 Webster]

            Shall he hot pull up the roots thereof, and cut off
            the fruit thereof, that it wither?    --Ezek. xvii.
                                                  9.
      [1913 Webster]

   2. To lose or want animal moisture; to waste; to pin? away,
      as animal bodies.
      [1913 Webster]

            This is man, old, wrinkled, faded, withered. --Shak.
      [1913 Webster]

            There was a man which had his hand withered. --Matt.
                                                  xii. 10.
      [1913 Webster]

            Now warm in love, now with'ring in the grave.
                                                  --Dryden.
      [1913 Webster]

   3. To lose vigor or power; to languish; to pass away. "Names
      that must not wither." --Byron.
      [1913 Webster]

            States thrive or wither as moons wax and wane.
                                                  --Cowper.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Withering \With"er*ing\, a.
   Tending to wither; causing to shrink or fade. --
   With"er*ing*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

withering
    adj 1: wreaking or capable of wreaking complete destruction;
           "possessing annihilative power"; "a devastating
           hurricane"; "the guns opened a withering fire" [syn:
           annihilative, annihilating, devastating,
           withering]
    2: making light of; "afire with annihilating invective"; "a
       devastating portrait of human folly"; "to compliments
       inflated I've a withering reply"- W.S.Gilbert [syn:
       annihilating, devastating, withering]
    n 1: any weakening or degeneration (especially through lack of
         use) [syn: atrophy, withering]

Moby Thesaurus II by Grady Ward, 1.0:

142 Moby Thesaurus words for "withering":
   Sanforizing, acerb, acerbate, acerbic, acid, acidic, acidulent,
   acidulous, acrid, acrimonious, air-drying, anhydration, arrogant,
   atrophy, attenuation, baneful, biting, bitter, calamitous,
   cataclysmal, cataclysmic, catastrophic, caustic, clannish,
   cliquish, coming apart, consuming, consumption, consumptive,
   contemptuous, contumelious, corroding, corrosive, cracking,
   crumbling, cutting, deadly, decadent, declining, degenerate,
   dehumidification, dehydration, demolishing, demolitionary,
   depredatory, desiccation, desolating, destroying, destructive,
   deteriorating, devastating, disastrous, disdainful, disintegrating,
   doomful, drainage, draining, drooping, drying, drying up,
   dwindling, ebbing, effete, emaceration, emaciation, evaporation,
   exclusive, fading, failing, falling, fatal, fateful, flagging,
   fragmenting, fratricidal, going to pieces, haughty, incisive,
   insolation, internecine, keen, languishing, marcescence,
   marcescent, mordacious, mordant, mummification, nihilist,
   nihilistic, parching, penetrating, piercing, pining, preshrinkage,
   ravaging, regressive, retrograde, retrogressive, ruining, ruinous,
   scathing, scorching, scornful, searing, self-destructive, sharp,
   shrinkage, shrinking, shriveling, sinking, sliding, slipping,
   slumping, sneering, sniffy, snobbish, snobby, snooty, snotty,
   stabbing, stinging, subsiding, subversionary, subversive, suicidal,
   supercilious, tabetic, tart, thinning, toploftical, toplofty,
   trenchant, vandalic, vandalish, vandalistic, waning, wastage,
   waste, wasteful, wasting, wilting, worsening